FIG. 2 is a schematic diagram illustrating a manufacturing method for a high-temperature superconductive oxide thin film by means of laser. In this method, a laser beam 1 oscillated from a laser device (not shown) such as a YAG laser device or an ArF excimer laser device is obliquely irradiated onto a target 2 provided with an oxide for formation of a thin film to cut the bond of particles constituting the target and simultaneously excite the particles to a high energy state. Then, a luminous region called a plume consisting of active evaporated particles is formed, and when the plume reaches a substrate 3 heated by a heater 4 or the like, a high-temperature superconductive thin film is obtained.
In general, it is considered to be desirable that an oxygen partial pressure during film formation is made high from the viewpoint of improvement in Tc end of a superconductive oxide thin film. However, when the oxygen partial pressure during film formation is high, the plume is reduced in shape, resulting in a low probability of reaching of the active particles to the substrate. To cope with this, it is considered that a distance between the target and the substrate is reduced to allow the plume to easily reach the substrate. However, this method cannot be adopted because it is necessary to define a given distance between the target and the substrate so as to irradiate the laser beam onto the target.
Accordingly, as an adoptable method, the oxygen partial pressure is reduced during film formation, and after forming the thin film, a post-treatment is carried out such as by cooling and maintaining the thin film in the atmosphere of oxygen to incorporate oxygen particles into the thin film, thereby improving Tc end.
In this method, however, when a crystal structure is modified from a tetragonal system to an orthorhombic system by the incorporation of the oxygen particles into the thin film, a twin plane is formed to relax a strain of a lattice constant. It is known that the twin plane generates a magnetic flux trap to cause a noise in case of practically applying the superconductive thin film to a superconductive device.